This application claims the priority of Germany Patent Document No. 199 10 080.2, filed Mar. 8, 1999, the disclosures of which is expressly incorporated by reference herein.
The invention relates to an adjusting device for a lengthwise adjustable vehicle seat with control arms for vertical adjustment of the seat.
In an adjusting device of this kind found in U.S. Pat. No. 2,919,744, control arms are provided on both sides at front and rear on lengthwise-adjustable support rails with, which arms a seat frame is articulated to the seat underframe. The corresponding lever arms of the front and rear control arms are each connected by links with one another, with each of the links comprising two coupling arms articulated to one another. The intermediate links of the total of four links are supported in a displaceably movable fashion on guide rails integral with the body. For vertical and lengthwise adjustment, a drive device with a drive fastened to the vehicle floor is provided, by which drive spindles running in the corresponding guide rails can be operated synchronously through associated drive cables. By means of the two spindles, the two intermediate links displaceably guided on the common guide rails are adjustable lengthwise along guide slots in the guide rails with the intermediate links being connected by an associated spindle nut that meshes with the spindle. The seat is adjusted lengthwise by the two spindles with an additional spindle associated with them being connected by a bracket with the lengthwise-adjustable support rails. To prevent lengthwise adjustment of the seat from taking place upon a vertical adjustment, the spindle nuts can be uncoupled from the associated brackets.
One of the disadvantages of this arrangement is that the vertical adjustment device is operated by a common drive device with the lengthwise adjustment device located on the body. This produces an adjustment device that requires a great deal of space, construction, and maintenance.
European Patent Document EP 0 238 234 A1 shows an adjusting device of this kind for vertical adjustment of the seat with control arms mounted on each side at the front and rear on the underframe of the seat, said arms having a link as the connection between the laterally corresponding control arms of the front and rear arms that requires a great deal of space especially in the comfort area of the seat cushion during its movement in the vertical adjustment of the vehicle seat. For coupling the four control arms, the front pair of control arms is nonrotatably connected with a manually drivable connecting rod. The links require a great deal of space during their movement in the vertical adjustment of the vehicle seat, especially in the comfort area of the seat cushion. To ensure adequate seating comfort for the occupants, the seat cushion part must be made relatively thick or located in a raised position relative to the seat frame.
A goal of the invention is therefore to provide an adjusting device of the above discussed general type, with a reduced space requirement and lower construction and maintenance costs.
This goal is achieved according to the invention by an adjusting device for a lengthwise adjustable vehicle seat comprising:
control arm units mounted on both sides at front and rear ends on a seat underframe for vertical adjustment of the vehicle seat, with which a seat frame is articulated on the seat underframe, corresponding control arms of the front and rear control arm units being connected with one another by a link assembly, each link assembly comprising two coupling arms articulated to one another at an intermediate joint supported so that it can move displaceably on the seat underframe, and a drive device operable to drive all the control arms in a pivotally movable fashion
wherein the intermediate joints are each displaceably guided on the seat underframe,
wherein the drive device for coupling the control arm units at opposite lateral sides of the seat comprises a transverse rod on which an associated pair of control arm units is nonrotatably mounted, and
wherein the drive device has a drive associated with it which is fastened to the seat underframe.
In the adjusting device according to the invention, each of the links comprises two coupling arms connected with one another with articulation, whose intermediate joint is supported on the lengthwise-adjustable seat underframe in a displaceably guided fashion. The drive for vertical adjustment, independent of the drive for lengthwise adjustment, moves together with the lengthwise-adjustable seat underframe and is fastened thereto, permitting a simple method of driving the adjusting device. For simple coupling of the four control arms that is as maintenance-free as possible, the front or rear driven pair of control arms is mounted nonrotatably on a transverse rod.
With this arrangement of the link lowered in the middle area, the comfort range of the seat cushion is increased and the support of the seat frame on the seat underframe is improved. In particular, the bending moments that act on the links during the vertical adjustment or in an accident are accepted not only by the support of the intermediate links on the seat underframe but also by the two-piece design of the links with the two coupling arms in an improved fashion. The intermediate links during their displacement movement can then travel in both a linear and an arcuate path.
A compensating link articulated between the front control arm and the seat frame serves in particular to receive forces acting on the seat frame, for example as a result of vibrations or vertical adjustment.
In addition, it has been found to be advantageous to mount the front and rear control arms pivotally on the associated lengthwise adjustable support rails of the seat underframe and to support the corresponding intermediate joints on the supporting rails, producing an especially good support for the seat frame on the seat underframe and an adjusting device that saves space in general.
In the particular case of an integral seat it has been found to be advantageous for the intermediate joints in each lengthwise adjusted position of the vehicle seat to be supported in the overlapping area with the guide rails that are integral with the vehicle. As a result, high forces that result for example from the tensile force of a belt on an integral seat in an accident and are introduced from the adjusting device through the support rails into the guide rails and then into the vehicle floor.
Finally, it has been found to be advantageous to provide laterally mounted relief springs to support the lifting movement of the seat frame in order in this way to relieve the load on the drive motor or provide it with smaller dimensions.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.